Method for manufacturing mask

ABSTRACT

Openings are formed in first and second mask layers. Next, diameter of the opening in the second mask layer is enlarged so that the diameter of the opening in the second mask layer becomes larger by a length X than diameter of the opening in the first mask layer. Thereafter, mask material is formed into the opening in the second mask layer, to form a cavity with a diameter X within the opening in the second mask layer. There is formed a mask which includes the second mask layer and the mask material having therein opening including the cavity.

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2009-295206, filed on Dec. 25, 2009, thedisclosure of which is incorporated herein in its entirety by reference.

TECHNICAL FIELD

The invention relates to a method for manufacturing a mask.

BACKGROUND ART

Conventionally, in the field of the semiconductor device, a hole formingmethod using a mask including a fine opening pattern has been studied.Japanese Patent Laid-Open No. 2009-238998 discloses the hole formingmethod. In this method, a film, a metal film, and a resist mask areformed on base material. Then, the metal film is subjected to dryetching using the resist mask, and, at the same time, the retreat amountof the resist mask by the dry etching is controlled, resulting informing opening with side surface which has first and second tiltangles.

Japanese Patent Laid-Open No. 2008-198991 discloses the hole formingmethod. This method comprises forming a first pattern, forming spacerson a side wall of the first pattern, forming a second pattern by fillingwith an insulating film into a gap between the spacers, removing thespacer in a contact hole region, and forming a contact hole by etchingusing the first and second patterns and the spacer.

Japanese Patent Laid-Open No. 2007-335628 discloses the method forforming the contact hole. In this method, a first resist film is formedon an insulating film, and, then, a second resist film is formed on thefirst resist film. Next, a first opening is formed in the second resistfilm using a first photolithography method and a second opening isformed in the first resist film using a second photolithography method,resulting in forming an overhang portion in the second resist film.Thereafter, a mortar-shape contact hole is formed in the insulating filmby selectively removing the insulating film using a reactive ion etchingmethod.

SUMMARY OF THE INVENTION

In one embodiment, there is provided a method for manufacturing a mask,comprising:

forming a second mask layer and a first mask layer in this order on afirst film;

patterning the first and second mask layers to form openings in thefirst and second mask layers;

enlarging diameters of the openings in the second mask layer so that thediameters of the openings in the second mask layer become larger thandiameters of the openings in the first mask layer;

depositing mask material into the openings in the first and second masklayers so that cavities are formed within the openings in the secondmask layer;

etching back the first mask layer and the mask material so that thesecond mask layer remains, to remove the first mask layer and to exposethe cavities in the second mask layer; and

removing the mask material from bottom surfaces of the cavities in athickness direction of the mask material until the first film isexposed, to form a mask which includes the second mask layer and themask material and has the openings including the cavities on the firstfilm.

In another embodiment, there is provided a method for manufacturing amask, comprising:

forming a second mask layer and a first mask layer in this order on afirst film, the second and first mask layers including therein openings;

performing an isotropic etching of the second mask layer so thatdiameters of the openings in the second mask layer become larger thandiameter of the openings in the first mask layer; and

removing the first mask layer so that the second mask layer remains andproviding mask material on side walls of the openings in the second masklayer so that cavities are formed in the openings in the second masklayer, to form a mask which includes the second mask layer and the maskmaterial and includes openings comprising therein the cavities.

BRIEF DESCRIPTION OF THE DRAWINGS

The above features and advantages of the present invention will be moreapparent from the following description of certain preferred embodimentstaken in conjunction with the accompanying drawings, in which:

FIG. 1A and FIG. 1B are views illustrating a method for manufacturing asemiconductor device according to a first exemplary embodiment of theinvention;

FIG. 2A and FIG. 2B are views illustrating the method for manufacturingthe semiconductor device according to the first exemplary embodiment ofthe invention;

FIG. 3A and FIG. 3B are views illustrating the method for manufacturingthe semiconductor device according to the first exemplary embodiment ofthe invention;

FIG. 4A and FIG. 4B are views illustrating the method for manufacturingthe semiconductor device according to the first exemplary embodiment ofthe invention;

FIG. 5A and FIG. 5B are views illustrating the method for manufacturingthe semiconductor device according to the first exemplary embodiment ofthe invention;

FIG. 6A and FIG. 6B are views illustrating the method for manufacturingthe semiconductor device according to the first exemplary embodiment ofthe invention;

FIG. 7A and FIG. 7B are views illustrating the method for manufacturingthe semiconductor device according to the first exemplary embodiment ofthe invention;

FIG. 8A and FIG. 8B are views illustrating the method for manufacturingthe semiconductor device according to the first exemplary embodiment ofthe invention;

FIG. 9A and FIG. 9B are views illustrating the method for manufacturingthe semiconductor device according to the first exemplary embodiment ofthe invention;

FIG. 10A and FIG. 10B are views illustrating the method formanufacturing the semiconductor device according to the first exemplaryembodiment of the invention;

FIG. 11A and FIG. 11B are views illustrating the method formanufacturing the semiconductor device according to the first exemplaryembodiment of the invention;

FIG. 12 is a view illustrating a semiconductor device according to asecond exemplary embodiment of the invention.

In the drawings, reference numerals have the following meanings: 1, 10:silicon substrate, 2, 11: interlayer insulating film, 3, 12: amorphouscarbon film, 4, 13: silicon oxynitride film, 5, 16: photoresist, 14:anti-reflection film, 15: organic film, 17: silicon oxide film, 18 a, 18b: opening, 18 c: first holes, 101: P type silicon substrate, 102:isolation region, 103: gate insulating film, 104: gate electrode, 105,106, 107, 108, 109: diffusion layers, 110, 111, 112: transistors, 113:first interlayer insulating film, 114, 115, 121, 130, 132: contact hole,116, 117, 131, 133: contact plug, 118: bit line, 119: firstinterconnection, 120: second interlayer insulating film, 122: capacitivecontact plug, 123: third interlayer insulating film, 124: cylinder hole,125: lower electrode, 126: capacitive insulating film, 127: upperelectrode, 128: fourth interlayer insulating film, 129: drawninterconnection, 134, 135: second interconnections, A: memory cellregion, B: peripheral circuit region, CH1, CH1 a, CH2, CH2 a: opening,R1, R2: diameter, X: diameter of cavities

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention will be now described herein with reference toillustrative embodiments. Those skilled in the art will recognize thatmany alternative embodiments can be accomplished using the teachings ofthe present invention and that the invention is not limited to theembodiments illustrated for explanatory purposes.

In addition, the exemplary embodiments below will be explained bydividing them into a plurality of sections or embodiments if necessaryfor convenience. They should not be construed as not being related toone another, and are in relations of modified embodiments of parts orthe entirety thereof, detailed explanation, and supplementalexplanations, etc., unless otherwise expressly described herein.

In a method for manufacturing a mask, openings are formed in first andsecond mask layers. At this time, there occurs variation between theopening diameters. Thereafter, by a diameter enlarging process, theopening diameters in the second mask layer become larger by a length Xthan the opening diameters in the first mask layer. Subsequently, maskmaterial is formed in the openings in the second mask layer. At thistime, the mask material is formed in the openings in the second masklayer until the openings in the first mask layer have been completelyburied with the mask material.

Herein, when the openings in the first mask layer is completely buriedwith the mask material, the amount of the mask material corresponding tothe opening diameters in the first mask layer is formed on inner wallsof the openings in the first mask layer. Thus, in the same manner, themask material with thickness corresponding to the opening diameters inthe first mask layer is also formed on inner walls of the openings inthe second mask layer.

As mentioned above, by the diameter enlarging process, the openingdiameters in the second mask layer become larger by the length X thanthe opening diameters in the first mask layer. Therefore, at the timewhen the formation of the mask material in the openings of the first andsecond mask layers has been finished up, the openings in the second masklayer are not completely buried with the mask material, resulting informing cavities having diameter of X in the second mask layer.Accordingly, although before or after the diameter enlarging process,there occurs variation between the opening diameters in the first andsecond mask layers, all of the cavities in the second mask layer becomethe same as the laterally etched amount X of the second mask layer bythe diameter enlarging process. That is, the diameters of the cavitiesbecome uniform. Thus, by using as a mask the second mask layer includingtherein the cavities as openings thereof and the mask material, it ispossible to manufacture the mask with opening pattern which has uniformopening diameter and is easy to control the opening diameter and issuitable to the miniaturization of the semiconductor device.

Below, exemplary embodiments of the invention will be described withreference to the drawings. Meanwhile, the following exemplaryembodiments are merely specific examples for making the inventionunderstood more deeply, and, accordingly, the invention is not limitedto such exemplary embodiments.

First Exemplary Embodiment

As shown in FIG. 1, interlayer insulating film 11 was formed on siliconsubstrate 10 using CVD method. Next, using CVD method, amorphous carbonfilm 12 (corresponding to a second film) with 200 nm thickness wasformed on interlayer insulating film 11. Then, silicon oxynitride film13 (corresponding to a first film) with 30 nm thickness was formed onamorphous carbon film 12. Using a spin coating method, organicanti-reflection film 14 (corresponding to a second mask layer) with 200nm thickness was formed on silicon oxynitride film 13. Then,silicon-containing organic film 15 (corresponding to a first mask layer)with 30 nm thickness was formed on organic anti-reflection film 14.After forming photoresist film 16 on silicon-containing organic film 15,an opening pattern with openings was formed by a lithography method in aregion corresponding to a semiconductor device formed in and on siliconsubstrate 10.

FIG. 1A is a top view of the opening pattern, and FIG. 1B is across-sectional view of the opening pattern taken at a line A-B of FIG.1A. Meanwhile, in the figures following FIG. 1, the semiconductor deviceformed in and on the silicon substrate 10 is omitted. Also, in thefigures following FIG. 1, the figures represented as the character “A”will be the top views of the opening pattern, and the figuresrepresented as the character “B” will be the cross-sectional views ofthe opening pattern taken at a line A-B of the associated top views.Depending on the figures, silicon substrate 10 and interlayer insulatingfilm 11 are omitted.

As shown in FIG. 1A, there occurs the variation between the openingdiameters in photoresist film 16, and, hence, the openings with twodifferent diameters were formed such as opening CH1 with diameter R1 andopening CH2 with diameter R2. For example, in case that using a liquidimmersion exposure apparatus employing ArF as its light source,variation in the opening diameters becomes ±8 nm, and, thus, a maximumdifference between the opening diameters becomes 16 nm.

As shown in FIG. 2A and FIG. 2B, the opening pattern was transferredinto silicon-containing organic film 15 by a dry etching method usingphotoresist film 16 and CF₄ gas as a mask and etching gas, respectively.This opening pattern has the opening diameters substantially equal tothe opening diameters in photoresist film 16.

As shown in FIG. 3A and FIG. 3B, after removing photoresist film 16, theopening pattern was transferred into organic anti-reflection film 14 bya dry etching method using silicon-containing organic film 15 as a mask.At this time, in organic anti-reflection film 14, there was formed theopening pattern with the opening diameters substantially equal to theopening diameters in silicon-containing organic film 15.

As shown in FIG. 4A and FIG. 4B, organic anti-reflection film 14 wassubjected to a dry etching using oxygen gas as etching gas (the diameterenlarging process). At this time, since the reaction level betweenorganic anti-reflection film 14 and oxygen radicals is high, organicanti-reflection film 14 was etched away in an isotropic way, so thatorganic anti-reflection film 14 was removed uniformly in a lateraldirection by constant amount X. As a result, in organic anti-reflectionfilm 14, openings CH1 with diameter R1 and openings CH2 with diameter R2became openings CH1 a with diameter R1+X and openings CH2 a withdiameter R2+X, respectively.

As shown in FIG. 5A and FIG. 5B, silicon oxide film 17 (corresponding tothe mask material) was deposited on an entire face of the resultantstructure by using ALD-CVD method, and was deposited into each ofopenings CH1 a, CH2 a. At this time, silicon oxide film 17 was depositedon the inner walls of the openings in organic anti-reflection film 14until the openings in silicon-containing organic film 15 have beencompletely buried with silicon oxide film 17. Herein, when the amount ofsilicon oxide film 17 corresponding to the opening diameters insilicon-containing organic film 15 has been formed on the inner walls ofthe openings in silicon-containing organic film 15, the openings insilicon-containing organic film 15 have been completely buried withsilicon oxide film 17.

Thus, in the same manner as in the openings in silicon-containingorganic film 15, there was formed silicon oxide film 17 with thicknesscorresponding to the opening diameters in silicon-containing organicfilm 15, on the inner walls of the openings in organic anti-reflectionfilm 14. Herein, by the previous diameter enlarging process, the openingdiameters in organic anti-reflection film 14 became larger by the lengthX than the opening diameters in silicon-containing organic film 15.Therefore, silicon oxide film 17 having thicknesses of R1/2 and R2/2 hadbeen deposited on the inner walls of openings CH1 a, CH2 a in organicanti-reflection film 14, respectively. Further, the openings in organicanti-reflection film 14 were not completely buried with silicon oxidefilm 17, so that cavities having diameter of X were formed in organicanti-reflection film 14.

Accordingly, although before or after the diameter enlarging process,there occurs variation such as R1 between the opening diameters inorganic anti-reflection film 14 and variation such as R2 between theopening diameters in silicon-containing organic film 15, all of thediameters of the cavities formed became the same as the laterally etchedamount X of organic anti-reflection film 14 by the diameter enlargingprocess (the laterally etched amount X corresponds to the differencebetween the opening diameters in organic anti-reflection film 14 and theopening diameters in silicon-containing organic film 15). That is, thediameters of the cavities became uniform.

As shown in FIG. 6A and FIG. 6B, by a dry etching method, silicon oxidefilm 17 was etched back, and, further, silicon-containing organic film15 was removed to form openings 18 a. All of openings derived fromopenings CH1 a, CH2 a had the same diameter as the length X which wasthe diameters of the cavities.

As shown in FIG. 7A and FIG. 7B, by a dry etching method, silicon oxidefilm 17 at bottom surfaces of openings 18 a was etched back and,further, an opening pattern with openings 18 b having diameter of X wasformed. An electronic micrograph of such formed opening pattern is shownin FIG. 8B. FIG. 8A is a graph showing variation (3σ) between theopening diameters in the opening pattern. As shown in FIG. 8A, thevariation (3σ) is 2, and, thus, such formed opening pattern has verysmall non-uniformity degree between the opening diameters.

As shown in FIG. 9A and FIG. 9B, using a dry etching, silicon oxynitridefilm 13 was etched away by etched amount Y/2. At this time, siliconoxide film 17 was also etched away by etched amount Y/2, resulting informing first holes 18 a having uniform diameter of X+Y.

As shown in FIG. 10A and FIG. 10B, after removing silicon oxide film 17and organic anti-reflection film 14, second holes 18 c were formed inamorphous carbon film 12 by a dry etching using silicon oxynitride film13 as a mask. At this time, since the diameters of the first holesformed in silicon oxynitride film 13 were uniform, it was possible toform the second holes which have uniform diameters and reach interlayerinsulating film 11 in amorphous carbon film 12.

As shown in FIG. 11A and FIG. 11B, after removing silicon oxynitridefilm 13, holes were formed in interlayer insulating film 11 by a dryetching using amorphous carbon film 12 as a mask. At this time, sincethe diameters of the second holes formed in amorphous carbon film 12were uniform, it was possible to form contact holes which have uniformdiameters and reach silicon substrate 10 in interlayer insulating film11.

As described above, according to the present exemplary embodiment, itwas possible to manufacture the mask with opening pattern which hasuniform opening diameter and is easy to control the opening diameter andis suitable to the miniaturization of the semiconductor device.

Second Exemplary Embodiment

This exemplary embodiment relates to a method for manufacturing a DRAMas a semiconductor device. This exemplary embodiment will be describedwith reference to a schematic cross-sectional view of FIG. 12. A lefthalf of FIG. 12 shows memory cell region A, while a right half of FIG.12 shows peripheral circuit region B.

After forming an isolation region 102 for identifying an active regionin P type silicon substrate 101, gate insulating films 103 were formedon the surface of the silicon substrate using a thermal-oxidationmethod. Next, conductive material was formed on the entire surface ofthe resultant structure using well-known CVD or sputtering methods.Then, gate electrodes 104 being word lines were formed by a well-knownlithography method and a dry etching method.

Subsequently, impurities such as phosphorus, arsenic, boron or the likewere implanted in the surface of silicon substrate 101 by an ionimplanting method using gate electrodes 104 as a mask, and, then, theresultant structure was subjected to heat treatment to form diffusionlayers 105, 106, 107, 108, and 109 being sources/drains.

In this way, in memory cell region A, transistors 110, 111 sharingdiffusion layer 106 with each other were formed, and, in peripheralcircuit region B, transistor 112 was formed.

Next, using well-known CVD or spin coating methods, first interlayerinsulating film 113 was formed on the entire surface of the resultantstructure so as to cover all of the transistors. Thereafter, the surfaceof the resultant structure was planarized using a well-known CMP method.Then, contact holes 114, 115 were formed using the method of theinvention. Contact holes 114 in memory cell region A were formed so asto expose portions of upper surfaces of diffusion layers 105, 106, 107formed in the silicon substrate. Contact holes 115 in peripheral circuitregion B were formed so as to expose portions of upper surfaces ofdiffusion layers 108, 109.

At the following, conductive material was formed on an entire surface ofthe resultant structure so as to fill contact holes 114, 115 withconductive material, and, then, the conductive material formed on theupper surface of first interlayer insulating film 113 was removed usinga CMP method to form contact plugs 116, 117.

Subsequently, a first interconnection layer was formed on an entiresurface of the resultant structure using CVD or sputtering methods, and,then, interconnections were formed by lithography and dry etchingmethods. In this manner, bit line 118 was formed in memory cell regionA, and first interconnection 119 was formed in peripheral circuit regionB.

Contact hole 114 was formed as hole for forming contact plug 116interconnecting the lower conductive layer including diffusion layer 106and the upper conductive layer including bit line 118 with each other.Contact holes 115 were formed as holes for forming contact plugs 117interconnecting the lower conductive layers including diffusion layers108 and 109 and the upper conductive layers including firstinterconnection 119 with each other. These contact holes 114, 115 wereformed in first interlayer insulating film 113 between silicon substrate101, and bit line 118 and first interconnection 119.

Next, using CVD or spin coating methods, second interlayer insulatingfilm 120 was formed on an entire surface of the resultant structure soas to cover bit line 118 and first interconnection 119. Thereafter, thesurface of the resultant structure was planarized using a CMP method.Then, in memory cell region A, contact holes 121 were formed using themethod of the invention. Contact holes 121 were formed so as to exposeportions of upper surfaces of contact plugs 116 in first interlayerinsulating film 113.

Subsequently, conductive material was formed on an entire surface of theresultant structure so as to fill contact holes 121 with conductivematerial. Then, the conductive material formed on the upper surface ofsecond interlayer insulating film 120 was removed using a CMP method,thereby forming capacitive contact plugs 122.

Then, using a CVD method, third interlayer insulating film 123 wasformed on an entire surface of the resultant structure. In order toincrease capacitances of capacitors due to increase of area of lowerelectrodes, thickness of third interlayer insulating film 123 was set tobe in a range of 2 to 3 μm. The third interlayer insulating film 123 hadthickness of four times or more than four times as large as thethicknesses of first and second interlayer insulating films 113, 120.After forming third interlayer insulating film 123, cylinder holes 124to be capacitors in memory cell region A were formed using the method ofinvention. Cylinder holes 124 were formed so as to expose portions ofthe upper surfaces of capacitive contact plugs 122 formed in secondinterlayer insulating film 120.

Thereafter, lower electrodes 125 was formed so as to cover the innersurfaces of cylinder holes 124, and, further, capacitive insulating film126 was formed on an entire surface of the resultant structure so as tocover lower electrodes 125. Then, upper electrode 127 was formed on anentire surface of the resultant structure so as to fill into remainingcavities within the cylinder holes. Next, upper electrode 127 andcapacitive insulating film 126 were patterned using lithography and dryetching methods. One portion of upper electrode 127 was drawn intoperipheral circuit region B so as to form drawn interconnection 129.

Contact holes 121 are holes for forming capacitive contact plugs 122interconnecting contact plugs 116 and lower electrodes 125 of thecapacitors with each other. Contact holes 121 were formed in secondinterlayer insulating film 120 between contact plugs 116 and lowerelectrodes 125 of the capacitors. Cylinder holes 124 were formed inthird interlayer insulating film 123 as holes for forming the capacitorsin a three-dimensional way.

Next, using a CVD method, fourth interlayer insulating film 128 wasformed on an entire surface of the resultant structure so as to coverupper electrode 127 and drawn interconnection 129 and, thereafter, thesurface of the resultant structure was planarized using CMP method.Then, in peripheral circuit region B, contact hole 132 was formed usingthe method of the invention. Contact hole 132 was formed so as topenetrate through the second to fourth interlayer insulating films andexpose portions of upper surfaces of first interconnections 119. At thistime, contact hole 130 exposing drawn interconnection 129 may be formedat the same time. Since contact hole 130 has a small depth, it ispossible to form it without using the method of the invention.

Subsequently, using a CVD method, conductive material was formed on anentire surface of the resultant structure so as to fill into contactholes 132, 130. Then, the conductive material formed on the uppersurface of the fourth interlayer insulating film was removed using a CMPmethod, thereby forming contact plugs 133, 131. Next, a secondinterconnection layer was formed on an entire surface of the resultantstructure using a sputtering method, and, then, second interconnections134, 135 were formed using lithography and dry etching methods.

Contact holes 132 was formed in a such way as to penetrate through thesecond to fourth interlayer insulating film between firstinterconnections 119 and second interconnection 135. Contact holes 132are holes for forming contact plug 133 interconnecting the lowerconductive layers including first interconnection 119 and the upperconductive layers including second interconnection 135.

As mentioned above, in manufacturing the semiconductor device, contactplug is required to interconnect lower conductive layer and upperconductive layer with each other. Accordingly, it is necessary to formthe contact holes having few variation between the diameters thereof inorder to improve reliability of the contact plugs, with high precision.

Further, in the DRAM including the capacitors, there are needs to formthe cylinder holes with a high aspect ratio (the smaller the diameterthereof and the larger the depth thereof, then, the higher the aspectratio thereof) or to form the contact holes for the peripheral circuitregion which are deeper than the cylinder holes. To deal with suchminiaturization of semiconductor device, employing of the liquidimmersion exposure apparatus using as its light source ArF laser withshort wavelength has been studied in the photolithography technique,and, now, it is possible to form a fine pattern with 60 nm or smallerthan 60 nm of a minimum processing dimension.

However, in the exposure apparatus including super-precise parts, therepotentially occurs certain variation between sizes in the resist patternformed by the exposure apparatus, and, further, as the pattern becomesfiner, relative ratio of the variation to an entire region of thepattern may increase. The inventor confirms in an experimental mannerthat the variation between the hole diameters comes into a substantialand explicit problem when the minimum processing dimension of thepattern becomes smaller than 50 nm.

In the present exemplary embodiment, although there appears variationbetween the opening diameters in the opening pattern formed in thephotoresist by the exposure, the variation may reduce in aself-alignment manner by using the method of the exemplary embodiment,to accomplish uniformity between the opening diameters. As a result,holes with uniform or constant diameters may be formed in layer to beopened. For this reason, the problem that bottom portions of the holesare not open or the problem resulting from the over-etching may beavoided. Furthermore, this exemplary embodiment can exhibit considerableeffect in particular when it is applied to forming of holes havingaverage diameters of 25 to 50 nm. If the average diameters are smallerthan 25 nm, it may be difficult to form the photoresist pattern andtransfer the photoresist pattern with high precision. If the averagediameters are larger than 50 nm, it has low probability that thevariation between the hole diameters come into the substantial andexplicit problem.

It is apparent that the present invention is not limited to the aboveembodiments, but may be modified and changed without departing from thescope and spirit of the invention.

In addition, while not specifically claimed in the claim section, theapplications reserve the right to include the following method formanufacturing a semiconductor device in the claim section at anyappropriate time:

1. A method for manufacturing a semiconductor device, comprising:

forming lower conductive layers;

forming an interlayer insulating film on the lower conductive layers;

forming a second mask layer and a first mask layer in this order on theinterlayer insulating film;

patterning the first and second mask layers to form openings atpositions corresponding to the lower conductive layers in the first andsecond mask layers;

enlarging diameters of the openings in the second mask layer so that thediameters of the openings in the second mask layer become larger thandiameters of the openings in the first mask layer;

depositing mask material into the openings in the first and second masklayers so that cavities are formed within the openings in the secondmask layer;

etching back the first mask layer and the mask material so that thesecond mask layer remains, to remove the first mask layer and to exposethe cavities in the second mask layer;

removing the mask material from bottom surfaces of the cavities in athickness direction of the mask material until the interlayer insulatingfilm is exposed, to form a mask which includes the second mask layer andthe mask material and has the openings including the cavities atpositions corresponding to the lower conductive layers on the interlayerinsulating film;

etching the interlayer insulating film using the mask, to form contactholes in the interlayer insulating film and beneath the openings of themask;

filling conductive material into the contact holes to form contactplugs; and

forming upper conductive layers so as to be electrically connected tothe contact plugs.

2. The method for manufacturing a semiconductor device according to theabove 1,

wherein diameters of the cavities are in a range of 25 to 50 nm.

3. The method for manufacturing a semiconductor device according to theabove 1,

wherein the first mask layer is a silicon-containing organic film.

4. The method for manufacturing a semiconductor device according to theabove 1,

wherein the second mask layer is an organic anti-reflection film.

5. The method for manufacturing a semiconductor device according to theabove 1,

wherein in enlarging the diameters of the openings in the second masklayer, the second mask layer is dry etched using oxygen gas as etchinggas.

6. The method for manufacturing a semiconductor device according to theabove 1,

wherein in forming the lower conductive layers, a MOS transistor isformed, the MOS transistor including source/drain regions as the lowerconductive layers.

7. The method for manufacturing a semiconductor device according to theabove 1,

wherein in forming the lower conductive layers, lower interconnectionlayers are formed as the lower conductive layers.

8. The method for manufacturing a semiconductor device according to theabove 1,

wherein in forming the upper conductive layers, upper interconnectionlayers are formed as the upper conductive layers.

9. The method for manufacturing a semiconductor device according to theabove 1,

wherein in forming the interlayer insulating film, at least oneinterlayer insulating layer is formed.

10. A method for manufacturing a semiconductor device, comprising:

forming lower conductive layers;

forming an interlayer insulating film, a second film, a first film, asecond mask layer, and a first mask layer in this order on the lowerconductive layers;

patterning the first and second mask layers to form openings atpositions corresponding to the lower conductive layers in the first andsecond mask layers;

enlarging diameters of the openings in the second mask layer so that thediameters of the openings in the second mask layer become larger thandiameters of the openings in the first mask layer;

depositing mask material into the openings in the first and second masklayers so that cavities are formed within the openings in the secondmask layer;

etching back the first mask layer and the mask material so that thesecond mask layer remains, to remove the first mask layer and to exposethe cavities in the second mask layer;

removing the mask material from bottom surfaces of the cavities in athickness direction of the mask material until the first film isexposed, to form a mask which includes the second mask layer and themask material and has the openings including the cavities at positionscorresponding to the lower conductive layers on the first film;

etching the first film using the mask, to form first holes in the firstfilm and beneath the openings of the mask;

removing the mask;

etching the second film using the first film as an mask for etching, toform second holes in the second film;

removing the first film; and

etching the interlayer insulating film using the second film as an maskfor etching, to form contact holes in the interlayer insulating film.

11. The method for manufacturing a semiconductor device according to theabove 10,

wherein the first film is a silicon oxynitride film.

12. The method for manufacturing a semiconductor device according to theabove 10,

wherein the second film is an amorphous carbon film.

13. A method for manufacturing a semiconductor device, comprising:

forming a second mask layer and a first mask layer in this order on afirst film;

patterning the first and second mask layers to form openings in thefirst and second mask layers;

enlarging diameters of the openings in the second mask layer so that thediameters of the openings in the second mask layer become larger thandiameters of the openings in the first mask layer;

depositing mask material into the openings in the first and second masklayers so that cavities are formed within the openings in the secondmask layer;

etching back the first mask layer and the mask material so that thesecond mask layer remains, to remove the first mask layer and to exposethe cavities in the second mask layer;

removing the mask material from bottom surfaces of the cavities in athickness direction of the mask material until the first film isexposed, to form a mask which includes the second mask layer and themask material and has the openings including the cavities on the firstfilm;

forming cylinder holes in the first film using the mask; and

forming lower electrodes, capacitive insulating films, and upperelectrodes in this order on inner walls of the cylinder holes, to formcapacitors.

14. The method for manufacturing a semiconductor device according to theabove 13,

wherein diameters of the cavities are in a range of 25 to 50 nm.

15. The method for manufacturing a semiconductor device according to theabove 13,

wherein the first mask layer is a silicon-containing organic film.

16. The method for manufacturing a semiconductor device according to theabove 13,

wherein the second mask layer is an organic anti-reflection film.

17. The method for manufacturing a semiconductor device according to theabove 13,

wherein in enlarging the diameters of the openings in the second masklayer, the second mask layer is dry etched using oxygen gas as etchinggas.

What is claimed is:
 1. A method for manufacturing a mask, comprising:forming a second mask layer and a first mask layer in this order on afirst film; patterning the first and second mask layers to form openingsin the first and second mask layers; enlarging diameters of the openingsin the second mask layer so that the diameters of the openings in thesecond mask layer become larger than diameters of the openings in thefirst mask layer; depositing mask material into the openings in thefirst and second mask layers so that cavities are formed within theopenings in the second mask layer; etching back the first mask layer andthe mask material so that the second mask layer remains, to remove thefirst mask layer and to expose the cavities in the second mask layer;and removing the mask material from bottom surfaces of the cavities in athickness direction of the mask material until the first film isexposed, to form a mask which includes the second mask layer and themask material and has the openings including the cavities on the firstfilm.
 2. A method for manufacturing a mask, comprising: forming a secondmask layer and a first mask layer in this order on a first film, thesecond and first mask layers including therein openings; performing anisotropic etching of the second mask layer so that diameters of theopenings in the second mask layer become larger than diameter of theopenings in the first mask layer; and removing the first mask layer sothat the second mask layer remains and providing mask material on sidewalls of the openings in the second mask layer so that cavities areformed in the openings in the second mask layer, to form a mask whichincludes the second mask layer and the mask material and includesopenings comprising therein the cavities.
 3. The method formanufacturing a mask according to claim 1, wherein diameters of thecavities are in a range of 25 to 50 nm.
 4. The method for manufacturinga mask according to claim 1, wherein the first mask layer is asilicon-containing organic film.
 5. The method for manufacturing a maskaccording to claim 1, wherein the second mask layer is an organicanti-reflection film.
 6. The method for manufacturing a mask accordingto claim 1, wherein in enlarging the diameters of the openings in thesecond mask layer, the second mask layer is dry etched using oxygen gasas etching gas.
 7. The method for manufacturing a mask according toclaim 2, wherein diameters of the cavity are in a range of 25 to 50 nm.8. The method for manufacturing a mask according to claim 2, wherein thefirst mask layer is a silicon-containing organic film.
 9. The method formanufacturing a mask according to claim 2, wherein the second mask layeris an organic anti-reflection film.
 10. The method for manufacturing amask according to claim 2, wherein in performing the isotropic etchingof the second mask layer, the second mask layer is dry etched usingoxygen gas as etching gas.